Phase Separation and Three-site Hopping in the 2-dimensional t-J Model

TL;DR

This paper investigates the impact of the three-site hopping term in the 2D t-J model, finding it does not alter the phase diagram qualitatively and identifying a critical J that varies linearly with temperature.

Contribution

It demonstrates that the three-site term has no qualitative effect on the mean field phase diagram of the t-J model and explores the temperature dependence of the critical coupling J.

Findings

The three-site term does not qualitatively change the phase diagram.

Phase coexistence occurs for J > J_c, consistent with experiments.

J_c decreases linearly with temperature, vanishing at T=0.

Abstract

We study the t-J model with the inclusion of the so called three-site term which comes out from the t/U --> 0 expansion of the Hubbard model. We find that this singlet pair hopping term has no qualitative effect on the structure of the pure mean field phase diagram for nonmagnetic states. In accordance with experimental data on high-T_c materials and some numerical studies, we also find wide regions of phase coexistence whenever the coupling J is greater than a critical value J_c. We show that J_c varies linearly with the temperature T, going to zero at T=0.